An Observational Study of Aerosol Optical Properties at the Top of Huangshan Mountains

The absorption and scattering coefficients of atmospheric aerosols were measured continuously using the Photo Acoustic Soot Spectrometer (PASS) during May to July in 2008 at the Guangmingding meteorological observatory on Huangshan Mountains. The characteristics of absorption and scattering coefficients, such as the diurnal variation and the relationships to meteorological factors were analyzed. The results show that, under the relative dry conditions (with the relative humidity lower than 60%), the absorption and scattering coefficients are larger during the daytime than that at night. It is found that both of these two coefficients are well correlated with relative humidity (with the correlation coefficients of 0.87 and 0.80, respectively), and are negatively correlated with the local wind speed (with the correlation coefficients of -0.53 and -0.78, respectively). It is also shown that both the absorption and scattering coefficients are remarkably reduced due to precipitation or fog. Compared with the properties measured in Nanjing, it is found that the values of absorption and scattering coefficients measured on Huangshan Mountains are order of magnitude smaller, and that the daily cycle is almost opposite to that in Nanjing. The possible reasons for this are explored.